Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
  • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
  • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
  • H04N21/433—Content storage operation, e.g. storage operation in response to a pause request, caching operations
  • H04N21/4334—Recording operations
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
  • G11B20/10—Digital recording or reproducing
  • G11B20/12—Formatting, e.g. arrangement of data block or words on the record carriers
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
  • G11B20/10—Digital recording or reproducing
  • G11B20/12—Formatting, e.g. arrangement of data block or words on the record carriers
  • G11B20/1201—Formatting, e.g. arrangement of data block or words on the record carriers on tapes
  • G11B20/1207—Formatting, e.g. arrangement of data block or words on the record carriers on tapes with transverse tracks only
  • G11B20/1208—Formatting, e.g. arrangement of data block or words on the record carriers on tapes with transverse tracks only for continuous data, e.g. digitised analog information signals, pulse code modulated [PCM] data
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
  • G11B27/10—Indexing; Addressing; Timing or synchronising; Measuring tape travel
  • G11B27/19—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier
  • G11B27/28—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier by using information signals recorded by the same method as the main recording
  • G11B27/30—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier by using information signals recorded by the same method as the main recording on the same track as the main recording
  • G11B27/3027—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier by using information signals recorded by the same method as the main recording on the same track as the main recording used signal is digitally coded
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
  • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
  • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
  • H04N21/4302—Content synchronisation processes, e.g. decoder synchronisation
  • H04N21/4305—Synchronising client clock from received content stream, e.g. locking decoder clock with encoder clock, extraction of the PCR packets
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N9/00—Details of colour television systems
  • H04N9/79—Processing of colour television signals in connection with recording
  • H04N9/80—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback
  • H04N9/804—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback involving pulse code modulation of the colour picture signal components
  • H04N9/8042—Transformation of the television signal for recording, e.g. modulation, frequency changing; Inverse transformation for playback involving pulse code modulation of the colour picture signal components involving data reduction
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B2220/00—Record carriers by type
  • G11B2220/90—Tape-like record carriers

Definitions

• the invention relates to an apparatus for recording a digital information signal on a record carrier, the digital information signal comprising a serial datastream of information packets, the information packets comprising a packet identifier and portions of information of one or more programs, packets having the same packet identifier belonging to the same program, the apparatus comprising:
• the digital information signal may be in the form of an MPEG transport stream, comprising packets that may occur irregularly in the transport stream.
• the ISO/IEC 13.818-1 international standard, part 1, 'Systems', document D5 in the list of related documents, comprise a description of the said transport stream, for transmitting a plurality of programs, for broadcasting purposes or for transmission via a cable network.
• Each program comprises one or more data compressed digital video signals and one or more corresponding data compressed audio signals.
• the transport packets in the transport stream comprise 188 bytes of information each.
• Packets in the MPEG serial data stream comprise, apart from 'system information', one kind of information, that is: either a portion of a video signal, or a portion of an audio signal or a portion of a data signal.
• a packet comprises information of only one of the video signals, or one of the audio signals or one of the data signals transmitted via the MPEG serial data stream.
• a transmission of such MPEG information signal in the form of a recording on and a reproduction from a record carrier require special measures to be taken in order to realize such kind of transmission.
• the above documents (Dl), D3 and D4 disclose the selection of one program, that is: one video signal and its corresponding audio signal(s), from the MPEG serial datastream for recording.
• transport packets will be selected on an irregular basis as a function of time.
• the earlier filed documents describe the measure to insert timing information (or a 'time stamp') in each of the packets recorded. Upon reproduction, the timing relation between the subsequent packets can be regained using the time stamps.
• document (Dl) disclose the generation of the time stamps in response to clock reference signals retrieved from packets in the serial datastream.
• Those clock reference signals defined as 'program clock reference' (PCR) in the above ISO/IEC standard, document (D5), occur (generally irregularly) in the MPEG datastream, are retrieved from the datastream and compared with the count value of a counter that is clocked by a 27 MHz clock comprised in the recording apparatus, so as to synchronize the said counter, by controlling the clock frequency of the 27 MHz clock.
• the said clock further clocks a second counter which generates the time stamps for combining to a corresponding packet.
• the invention aims at providing a recording apparatus for recording a plurality of programs, each program comprising a video signal with its corresponding audio signal(s).
• the recording apparatus as defined in the opening paragraph is characterized in that the retrieval means are adapted to (d) detect the presence of a clock reference signal in the packets in the serial datastream of information packets, (e) retrieve the packet identifier from the first packet in which a clock reference signal has been detected and store the packet identifier retrieved from that packet in a memory,
• step (f) subsequently retrieve clock reference signals from those packets having a packet identifier which equals the packet identifier stored in the memory, (g) monitor the time interval since the last occurrence of a clock reference signal in/from those packets having a packet identifier which equals the packet identifier stored in the memory, (h) return to step (d) upon the said time interval exceeding a predetermined time interval.
• the invention is based on the recognition that, for recording one program, comprising a video signal and its corresponding audio signal(s), the packets comprising information corresponding to this video signal and its corresponding audio signal(s) can be found via the program allocation table (PAT) included in the datastream.
• the program allocation table is included in packets in the MPEG transport stream.
• the program allocation table comprises for each program included in the transport stream a pointing vector to packets having a specific PID value.
• Those packets comprise the program map table (PMT) for the said program.
• the program map table comprise, amongst others, the values of the packet identifier of those packets that comprise the program clock reference signals for the said program. In this relatively complicated way, the program clock reference signals can be located in the MPEG datastream and retrieved therefrom.
• a simpler way of detecting the program clock reference signals is carried out, namely by not using the program allocation table and the program map table, but simply by checking every packet that passes by for the presence of a program clock reference signal.
• One of the program clock reference signals of the programs selected for recording will be chosen, namely that one program clock reference signal that has been detected first.
• the program clock reference chosen for generating the time stamps during recording of the programs is an arbitrary one of the program clock references corresponding to the programs selected for recording.
• figure 1 shows the information signal to be recorded as a function of time, comprising packets that occur irregularly as a function of time
• figure 2 shows the contents of a packet in the MPEG datastream
• figure 3 shows the content of another packet, comprising an adaptation field and a PCR signal in the adaptation field
• figure 4 shows a schematic embodiment of the recording apparatus
• figure 5 shows a flow diagram of the method for retrieving the PCR values
• figure 6 shows a more elaborated embodiment of the retrieval unit in the recording apparatus.
• Figure 1 shows schematically the serial datastream of an MPEG encoded digital transport stream, selected for recording on the record carrier and figure 2 shows schematically the contents of a packet comprised in the serial datastream.
• the packets comprise 188 bytes of information each.
• Each packet comprises a header portion, denoted 'HDR', of 4 bytes long and a datafield, denoted 'DATA', which is 184 bytes long, for storing a portion of information of the digital video signal or the digital audio signal, or for storing data.
• a packet comprises information of one kind of signal, either a video signal, or an audio signal, or a data signal.
• a sync word, denoted 'SYNC, and a packet identifier number (PID) are included in the headers of the packets, see figure 2.
• the packet identifers (PID) identify the kind of information included in a packet. Packets having the same PID comprise the same information stream.
• the header portion HDR further comprises a 2-bit adaptation field control word, denoted 'AFC. When the value of the AFC equals '01', the packet is as shown in figure 2. When the value of AFC equals '11', the packet is in the form as shown in figure 3.
• the 184 byte long datafield of figure 2 is now subdivided into a first portion, denoted 'AF', the so-called adaptation field, and the remaining portion, again denoted 'DATA' is for storing a portion of information of the digital video signal or the digital audio signal, or for storing data.
• 'AF' the so-called adaptation field
• 'DATA' the remaining portion
• the length of the adaptation field can be variable. Therefore, the adaptation field comprises a word AFL, indicating the adaptation field length.
• the adaptation field length word AFL is the first byte in the adaptation field.
• the adaptation field AF comprises a flag, denoted 'PCR flag' (program clock reference flag), at a specific fixed position in the adaptation field.
• the datastream shown in (a) of figure 1 as a function of time is the datastream comprising only those (one or more) programs that have been selected from an incoming MPEG transport stream, for recording in the recording apparatus to be described later on the record carrier.
• the datastream comprises packets P ⁇ P 2 , P 3 , ....
• the PID values for the packets are given in (a) of figure 1, above the packets in question.
• the packet P 2 has a PID value of 110
• the packet P 2 has a PID value of 112
• the packet P 3 has a PID value of 101, and so on.
• the first program is the program comprising the datastreams of packets having PID values 110 and 112 and the second program comprises the datastreams of packets having PID values 101 and 103.
• the datastream of packets having a PID value equal to 110 can be a datastream of a video signal.
• the datastream of packets having the PID value equal to 112 can be the datastream of the corresponding audio signal.
• the datastream of packets having a PID value equal to 101 can be a datastream of a video signal.
• the datastream of packets having the PID value equal to 103 can be the datastream of the corresponding audio signal.
• the datastreams of the video signals have their own program clock reference signals stored, generally irregularly, in some of the packets in the respective datastreams.
• those packets comprising a program clock reference signal are indicated by an 'x'.
• FIG. 4 shows a schematic embodiment of the recording apparatus.
• the apparatus comprises an input terminal 10 for receiving the datastream shown in (a) of figure 1.
• the input terminal is coupled to a first input of a signal combination unit 12 and to an input of a retrieval unit 14.
• the retrieval unit 14 is adapted to retrieve the PCR signals from the packets of the serial datastream shown in (a) of figure 1.
• the PCR signals retrieved are supplied to a terminal denoted 'a' of a controllable switch S, via its output 28.
• a memory 26 is available and coupled to the retrieval unit 14, for storing a PID value. Further, a timer 30 is available for cooperating with the retrieval unit 14, as will be made clear hereafter.
• a terminal 'c' of the switch S is coupled to an input of a counter 20.
• a 42-bit wide output 21 of the counter 20 is coupled to a first input of a comparator 16.
• the 'b' terminal of the switch S is coupled to a second input of the comparator 16.
• An output of the comparator 16 is coupled to a control input of a controllable oscillator 22, which preferably runs at a 27 MHz frequency on the average.
• the output of the oscillator 22 is coupled to clock inputs of the counters 20 and 24.
• the counter 24 has a 22-bit wide output which is coupled to a second input of the signal combination unit 12.
• An output of the signal combination unit 12 is coupled to an input of a write unit 18.
• the write unit 18 is well known in the art and needs no further explanation.
• the counter generates the time stamps for the packets, which time stamps are combined to their corresponding packets in the signal combination unit 12. Further, a central processing unit 84 is present, amongst others, for controlling the position of the switch S.
• the retrieval unit 14 looks for the presence of the AFC word in the header portion HDR of the packets. If the retrieval unit 14 detects a packet having an AFC word equal to '10' or '11', it knows that an adaptation field is present in the said packet. It subsequently looks for the value of the PCR flag in the adaptation field. If the PCR flag has a value '1', it knows that a PCR signal is present in the adaptation field AF.
• the switch S is switched into its position a-c. Therefore, the PCR signal retrieved is supplied to the counter 20 and stored therein so as to set the counter to a count value equal to the PCR value.
• the retrieval unit 14 switches into a mode in which the search for PCR signals is restricted to only the packets having a PID value that is equal to the PID value stored in the memory 26.
• the switch S is switched into its position a-b.
• the packet further comprises a PCR value
• this value is retrieved from the packet and supplied, via its output 28, to the comparator 16.
• the comparator 16 compares the PCR value with the count value supplied by the counter 21 and generates a control signal in response to the difference between both values.
• the control signal controls the oscillator 22 by either slowing it down or speeding it up, so as to bring the PCR values supplied to the second input of the comparator 16 is agreement with the count values supplied by the counter 20 to the first input of the comparator 16.
• the timer 30 measures the length of the time interval since the last occurrence of a PCR value detected by the retrieval unit 14. When the time interval measured by the timer 30 exceeds a specific predetermined time interval, the retrieval unit 14 is switched into its original detection mode, in which all the packets are checked for the presence of a PCR value, and the switch S is switched into its position a-c.
• the retrieval unit 14 looks for the presence of a PCR value in the packet ? ! and finds no PCR value. Next, it checks the packet P 2 for the presence of a PCR value. Again, it finds no such PCR value. Next, it finds a PCR value in the packet P 3 .
• the PID value which equals 101, is stored in the memory 26. Further, the PCR value is outputted at its output 28 and, as the switch S is in its position a-c, the PCR value is supplied to the counter 20 so as to set the count value of the counter 20 to a count value corresponding to the PCR value.
• the retrieval unit 14 does not retrieve the PCR value in the packet P 7 , as the PID number is not the same as the PID stored in the memory 26.
• the retrieval unit 30 Upon receiving the packet P 10 at the input 10, the retrieval unit 30 detects a PID number which is equal to the PID number stored in the memory 26 and subsequently retrieves the PCR signal stored in the said packet and supplies the PCR signal to its output 28.
• the comparator 16 compares the PCR value just retrieved with the count value supplied by the counter 20 and generates a control signal so as to control the frequency of the oscillator 22.
• recording of the various datastreams is realized using time stamps generated on the basis of the PCR signals retrieved from the datastream having the PID number 101.
• the retrieval unit 14 looks for the presence of a PCR value in the packet P 5 and finds no PCR value. Next, it checks the packet P 6 for the presence of a PCR value. It finds no PCR value in the packet P 6 . Next, the retrieval unit 14 detects a PCR value in the packet P 7 .
• the PID value which equals 110, is stored in the memory 26 and the PCR value is outputted at its output 28 and supplied to the counter 20 via the switch S, so as to set the count value in the counter 20 to a count value corresponding to the PCR value detected.
• the retrieval unit 14 does not retrieve the PCR value in the packet P 10 as the PID number of this packet is not the same as the PID stored in the memory 26.
• the retrieval unit 14 Upon receiving the packet P 16 at the input 10, the retrieval unit 14 detects a PID number which is equal to the PID number stored in the memory 26 and subsequently retrieves the PCR signal stored in the said packet and supplies the PCR signal to its output 28.
• the PCR value is supplied to the second input of the comparator 16 and compared therein with the count value of the counter 20.
• the control signal generated by the comparator 20 in response thereto is used to control the frequency of the oscillator 22.
• recording of the various datastreams is realized using time stamps generated on the basis of the PCR signals retrieved from the datastream having the PID number 110.
• block 50 the recording of the transport stream shown in (a) of figure 1 is started.
• a packet is inputted in the retrieval unit 14, block 52 in figure 5.
• the retrieval unit 14 looks for the presence of a PCR signal in the packet, and if not, the program returns to block 52, by inputting the next packet. If so, see block 54, the PID value comprised in the packet is retrieved, block 56, and stored in the memory 26, block 58. Further, the PCR value is retrieved from the packet, block 60.
• the next packet is inputted, block 62. If a PCR signal is present in the packet, see block 64, and the PID of the packet equals the PID value stored in the memory, see block 66, the PCR signal is retrieved from the packet, see block 60. If no PCR value is present in the packet, see block 64, or if the PID value is not the same as the PID value stored in the memory 26, the program returns to block 68.
• FIG. 6 shows a more elaborated version of the retrieval unit 14 in the recording apparatus.
• the retrieval unit 14 comprises a memory 80, having an input coupled to the input 27 of the retrieval unit 14.
• the memory is in the form of a shift register in which at least the head portion of a packet can be stored, in figure 6 in the reverse order compared to the order of the packet shown in figure 2 and 3.
• Various parallel outputs of the memory 80 are available.
• the last 8 storage positions in the memory can form a first output 82, which may be coupled to an input of a central processor unit CPU 84.
• a second output of the memory 80 is the output 86, which is coupled to corresponding inputs of a comparator 88 and the memory 26.
• An output of the memory 26 is coupled to a second input of the comparator 88.
• a third output 90 of the memory 80 is coupled to an input of a first detector 92.
• a fourth output 94 is coupled to an input of a second detector 96.
• another output 98 of the memory 80 is coupled to the output 28 of the retrieval unit 14.
• Outputs of the detectors 92 and 96 are coupled to corresponding inputs of an AND circuit 100, which has an output coupled to control inputs 102 and 104 of the CPU 84 and the memory 26 respectively and to an output 106.
• a switch 108 which is controlled by a control signal from the CPU 84, is included in the connection between the output of the AND circuit 100 and the control input 104 of the memory 26.
• An output of the comparator 88 is coupled to an input 112 of the CPU 84.
• the timer 30 is coupled to the CPU 84.
• the timer output is coupled to one input of a comparator 120, which receives a value corresponding to the predetermined time interval T at a second input.
• the time interval T could be chosen equal to 100 ms.
• An output of the comparator 120 is coupled to a control input 122 of the CPU. The functioning of this retrieval unit is as follows. Upon starting recording, the CPU is instructed to generate a control signal at its output 110 to supply a control signal to the switch 108 so that it closes.
• the CPU 84 can detect the byte stored in the said 8 bit positions as being equal to the sync word. If so, this means that at the output 86 of the memory 80, the PID value of the packet is available and that at the output 90, the AFC word is available. If the packet comprise an adaptation field, this further means that at the output 94 of the memory 80, the PCR flag is available and that, if the said flag equals '1', the PCR signal is available at the output 98.
• the CPU Upon detecting the sync word at the output 82, the CPU instructs the detector 92 to check whether the AFC word equals '10' or '11'. If so, this means that an adaptation field is present in the packet, and the detector 92 generates a control signal at its output. Further, the CPU instructs the detector 96 to check whether the PCR flag equals '1'. If so, this means that the adaptation field comprise a PCR signal, and the detector 96 generates a control signal at its output. Upon receiving control signals at both inputs, the AND circuit 100 generates a control signal at its output. Upon receipt of the control signal, the memory 26 stores the PID value applied to its input in the memory.
• the CPU in response to the control signal, the CPU generates a control signal at its output 110 so as to open the switch 108. Further, via the output 106, the counter 20 can be controlled so as to accept the PCR signal present at the output 28 of the retrieval unit 14, and supplied to the counter 20 via the switch S, see figure 4.
• the PID value stored in this packet and supplied to the comparator 88 is compared to the PID value stored in the memory 26.
• the comparator supplies a control signal to the input 112 of the CPU 84, and in response thereto, the CPU disables the detectors 92 and 96.
• the comparator 88 Upon agreement between the two PID values, the comparator 88 generates another control signal, which is supplied to the CPU.
• the CPU enables the detectors 92 and 96, so that they can generate a control signal if the AFC word equals '10' or '11' and the PCR flag equals ' 1'. If both control signals occur, the AND circuit 100 again generates a control signal which is supplied to the output 106, so that the PCR signal present at the output 28, can be supplied to the second input of the comparator 16, in response to this control signal, see figure 4.
• the timer 30 is each time restarted and measures the time since the last occurrence of a PCR value in the packets having a PID equal to the PID stored in the memory 26. If the time interval measured in the timer 30 exceeds the time interval T 0 , the comparator 120 generates a control signal at its output. In response to this control signal, the CPU again closes the switch, and the search for the next PCR value starts again, as explained above.
• the invention has been described with reference to preferred embodiments thereof, it is to be understood that these are not limitative examples. Thus, various modifications may become apparent to those skilled in the art, without departing from the scope of the invention, as defined by the claims. As an example, the invention has been described with reference to the generation of time stamps. The choice and detection of the PCR values could however be used for other purposes, such as for locking a tape servo system to the PCR values in the transport stream.

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• Engineering & Computer Science (AREA)
• Signal Processing (AREA)
• Multimedia (AREA)
• Signal Processing For Digital Recording And Reproducing (AREA)
• Television Signal Processing For Recording (AREA)
• Indexing, Searching, Synchronizing, And The Amount Of Synchronization Travel Of Record Carriers (AREA)
• Management Or Editing Of Information On Record Carriers (AREA)

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• 1998
  • 1998-02-27 EP EP98903231A patent/EP0904585A2/de not_active Withdrawn
  • 1998-02-27 WO PCT/IB1998/000246 patent/WO1998040889A2/en not_active Application Discontinuation

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